Focal areas of hemorrhagic necrosis will be produced in the brains of anesthetized monkeys by freezing with liquid nitrogen. The accompanying cerebral edema will be studied with the computerized tomographic (CT) brain scan and chemical analysis of the tissue. An attempt will be made to correlate chemical changes in tissue with changes in the CT numbers. The brains of patients with cerebral edema who have had a CT scan within 24 hrs. prior to death will be studied by histologic techniques. This will involve the mapping of histological changes in whole brain sections and correlation both with the CT image and CT numbers. The aim of this project is to define an accurate reproducible method for the quantitative measurement of cerebral edema in the living subject utilizing CT data.